The present invention relates to a display device for use in portable equipment, an electronic memo and the like which has a function such as pen input.
FIG. 5 shows a schematic structure of a conventional display device. As shown in FIG. 5, in a mounting structure of a conventional display device, a film substrate TCP (Tape Carrier Package) 8 provided with a slit for folding it down is used, and terminals of a display element 1 is connected with terminals of the TCP 8. An IC 4 is mounted on the TCP, and further, the TCP is connected with a circuit substrate such that fabrication is carried out with the TCP folded down and with the circuit substrate located on the rear surface of the display element. As the circuit substrate, a glass epoxy substrate, a polyimide film substrate or the like with chip parts mounted thereon has been used.
FIG. 6 shows a schematic view of a COF (Chip On FPC) structure with the IC 4 directly mounted on the film substrate 2. In a COF structure, the above-mentioned TCP circuit and the circuit of the circuit substrate are formed on a single film substrate.
However, in the structure shown in FIG. 5, since the TCP 8 is provided with a slit for folding down, and the folding down at the slit portion is carried out after the TCP 8 in a flat state is connected with the terminals of the display element 1 by thermocompression bonding, there is a problem that a margin 9 for folding down the TCP goes beyond the outer shape of the display device, resulting in larger size of the outer shape.
Further, depending on the direction of the folding down, the IC 4 and other electronic parts mounted on the film substrate are located between the film substrate and the display element. In that case, restriction with regard to the thickness of the whole film substrate increases in designing electronic equipment in which the display element is to be incorporated.
In the COF structure shown in FIG. 6, though the problem of parts location can be dealt with by a through hole, since the number of output electrodes of the IC 4 which is a driver IC is large, and the terminal connection pitch is fine, a through hole area 10 increase, which either decreases the parts mounting area or enlarges the outer shape of the film substrate, leading to increased design restriction.
Further, in case the connection between terminals of the film substrate and of the display element is structured as shown in FIG. 7, there arises design restriction with regard to a margin for folding down the film 2 and with regard to the through hole area.
Further, in case a COF formed of a single film substrate is connected with a display element where terminals are disposed on respective transparent substrates facing to each other, connection with one of the transparent substrates can be carried out, while connection with the other of the transparent substrates facing the one of the transparent substrates is very difficult in a compression bonding process. Therefore, in this case, the COF must be prepared for the terminals of the respective transparent substrates forming the display element.
Further, though an I/F cable may be connected with a circuit substrate as a discrete part, in case of a COF, the I/F cable is formed of FPC itself so as to be T-shaped or L-shaped. Because of the shape, the number of the COFs which can be taken from the material is small.
Accordingly, objects of the present invention are to make smaller the size of the outer shape of a margin portion for folding down a film substrate, to materialize a structure where a single film substrate can be easily connected with a plurality of sides of a display element, and to make larger the number of film substrates which can be taken from the material by improving the layout of I/F cables.